1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording, for use in a perpendicular magnetic recording-type magnetic recording device.
2. Related Background Art
High densification of recording media for magnetic recording devices is achieved using perpendicular magnetic recording systems wherein magnetic information is recorded in the direction perpendicular to the recording surfaces of the recording media, and magnetic heads for perpendicular magnetic recording are employed for the recording on the recording media.
Recording media for perpendicular magnetic recording systems include double-layer recording media comprising a recording layer and a soft magnetic back layer, and single-layer recording media having no back layer. When using a double-layer recording medium, it is necessary to carry out magnetic recording on the recording medium using a magnetic head which comprises a magnetic pole and a return yoke.
To achieve higher recording density, on the other hand, it is preferred to increase not only the linear recording density of the recording medium, but also to narrow the width of the pole tip to increase the track density. However, when the pole tip is narrowed, remanent magnetization occurs as a result of shape anisotropy at the magnetic pole, and therefore when magnetic information is recorded in the recording medium using the recording head, the magnetization recorded in the recording medium is erased by the remanent magnetic field arising from the remanent magnetization, resulting in the problem of erasure of the magnetic information, or “pole erasure”. It is ordinarily thought that the problem of pole erasure is attributed to the increased influence of shape anisotropy at the pole tip when the width of the pole tip is narrowed.
In order to eliminate the problem of pole erasure, there has been proposed a magnetic head having a main magnetic pole with a constricted section in which the cross-sectional area parallel to the air bearing surface (the side facing the recording surface of the recording medium) decreases toward the air bearing surface CABS), the structure being such that the ratio between the distance from the position of the constricted section nearest the air bearing surface to the main magnetic pole air bearing surface and the area of the main magnetic pole air bearing surface is larger than 0 and smaller than 0.002 [nm−1] (see Japanese Unexamined Patent Publication No. 2003-296906).
It is noted that uniaxial magnetic anisotropy thin-films or magnetic thin-films are disclosed in Japanese Unexamined Patent Publication HEI No. 7-86035, Japanese Unexamined Patent Publication HEI No. 9-82522 and Japanese Unexamined Patent Publication HEI No. 7-86038.